HIV Drug groups - Protease inhibitors

Protease inhibitors (PIs) are a class of medications used to treat or prevent infection by viruses, including HIV and Hepatitis C. PIs prevent viral replication by inhibiting the activity of HIV-1 protease, an enzyme used by the viruses to cleave nascent proteins for final assembly of new virons.

Protease inhibitors have been developed or are presently undergoing testing for treating various viruses:

HIV/AIDS: antiretroviral protease inhibitors such assaquinavir, ritonavir, indinavir, nelfinavir etc.

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Saquinavir

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Saquinavir is an antiretroviral drug used in HIV therapy. It falls in the protease inhibitor class. Two formulations have been marketed:

a hard-gel capsule formulation of the mesylate, with trade name Invirase®, which requires combination with ritonavir to increase the saquinavir bioavailability; a soft-gel capsule formulation of saquinavir, with trade name Fortovase®. Both formulations are generally used as a component of highly active antiretroviral therapy (HAART). Ritonavir

Ritonavir, with trade name Norvir® (Abbott Laboratories), is an antiretroviral drug from the protease inhibitor class used to treat HIV infection and AIDS.

Ritonavir is frequently prescribed with HAART, not for its antiviral action, but as it inhibits the same host enzyme that metabolizes other protease inhibitors. This inhibition leads to higher plasma concentrations of these latter drugs, allowing the clinician to lower their dose and frequency and improving their clinical efficacy.

Indinavir

Indinavir (IDV; trade name Crixivan, manufactured by Merck) is a protease inhibitor used as a component of highly active antiretroviral therapy (HAART) to treat HIV infection and AIDS.

Nelfinavir

Nelfinavir (Viracept®) is an antiretroviral drug used in the treatment of the human immunodeficiency virus (HIV). Nelfinavir belongs to the class of drugs known as protease inhibitors (PIs) and like other PIs is generally used in combination with other antiretroviral drugs. Nelfinavir is presented as the mesilate (mesylate) ester prodrug.

Nelfinavir mesylate (Viracept, formally AG1343) is a potent and orally bioavailable human immunodeficiency virus HIV-1 protease inhibitor (Ki=2nM) and is being widely prescribed in combination with HIV reverse transcriptase inhibitors for the treatment of HIV infection. Nelfinavir mesylate contains the Castor oil derivative Cremophor EL

Treatment for HIV

At present treatment for HIV infection involves using a combination of drugs. One type of drug inhibits nucleic acid replication, for example, when AZT is incorporated into DNA by reverse trasncriptase, no additional nucleotides can be added.

A second class of drugs inhibits a protease involved in cleaving large polyproteins into functional segments. When the protease is inhibited, virus particles cannot be produced Use of a combination of drugs directed at different targets reduces the likelihood of the development of resistance by mutation.

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Research is underway to develop new treatments for HIV. Chemicals called chemokines appear to inhibit HIV infection by binding to and blocking the CXCR4 and CCR5 co receptors on the host cells.

A search is in progress to apply such chemicals in HIV treatment,Some individuals who are HIV positive, but did not develop AIDS have a mutation in the CCR5 receptor that makes it defective.

Research is in progress to determine whether disabling the CCR5 receptor might beeffective in controlling AIDS in infected patients.An antiviral factor called CAF is found in CD8 cells.Research is in progress to determine if this substance could be used to block replication of HIV.

There is currently no approved vaccine against HIV infection. One problem is that HIVsurface proteins such as gp120 mutate at a high rate.Scientist may be able to construct a vaccine using an HIV with a defective form of the viral gene nef.

Viruses with the defective nef gene seem to have reduced reproductive capability, allowing the immune system to keep the virus in check.